Vacuum tube circuits



March 8, 1932. c. E. STRONG VACUUM TUBE CIRCUITS Filed Sept. 11, 1950 2sheetssh et 1 FIG] INVENTO/P C. E. STRONG A ORNEY M h 1, v c. E. STRONG1,348,209

VACUUM TUBE CIRCUITS Filed Sept. 11, 1930 2 Sheets-Sheet 2 J B) WmPatentecl Mar. 8, 1932 mcoaronn'rnn, OF NEW YORK,-N.

Y., A conronnrron or NEWVYORK VACUU BE CIRCUITS I Application filed setembern, 193o,:s a1 No.

This invention relates to Wave translation systems vand particularly toamplifying circuits utilizing electron dischargetubes.

Hitherto in amplifying systems it has been if usuaL-When greatamplificationthas beenrequired, 'to connect a number of vacuum tubes finparallell I A difficulty experienced "in such arrangements has been toprovide for thegrid excitation to be equal on each of the tubesandforeach'tubeto Work" into as1milar plate impedances This has beenparticue V larly noticeable insystemsg for amplifying,

very high frequencies of the order of meg: acycles and it has beenproposed to mount lliithetubesivery closetogether to overcome thisd-ifliculty but due to the'close proximity ofithe tubes undersuchconditions spurious oscilla- I tions' have been set 1113:(1116 tothe mtercou p'ling'between the tube electrodes. Up'tothe 20* presenttherefore; there has been :a; limit to 1 v the number of tubes Which-maybe connected, in parallel-, \vhich'for the *very high frequen- I ,ciesalready referred to has been. about three or. four and this'obviouslylimits the total amplification it is possibleto obtain."

5 In order't'o increasethe nun'iber oftubes and thus the possibility ofhandling greateri wh ch the grld' 'circuitsaretuned The anode power, ithas also been proposed to arrange in push-pull two sets of parallelconnected tubes. While this arrangement certainly doubles the limit ofthe number-oftubes it is-possible to use, there has also been a limit Iin this arrangement which limit for very high frequ'enciesf hasbeen"sixfor eight, that is,

"three, or fourinreac'hpart of the puslrpull arrangement. 7

Itis an object of the present invention,

therefore,-to increase substantially the "num- P ber oftubesitis'possible to use without encountering the above mentioneddifiiculties. In accordance with a feature of the'present invention, aplurality of groups of tubescoin 'nected inpushpull are arranged toimpress their power intoan output circuit? common "toall of them, eachgroup being arranged to impress itspower ata'n anti-nodal voltage pointdifferent to'that at Whichthe other groups impress their, outputs. 1This and other features of the invention will be explained by the aid oftheaccom- 481,094, and in Great BritainJDecembere,1929;

panying drawings which show development of the invention.

Figs. 1 and 2 showthe essentials of known forms of push-pull circuitsusing :three elec-i trode valves, for facilitating explanation of;

the invention; I

Fig. 3 showsan embodiment of-the present invention;. i

iig'. 4 shows a of-Fig.3; I I I.

I Fig. '5 is a simplifieds'howing of thesysa tem of F ig. 3Wll3l1"certain elements omitted forsi'mplicitymndj 1 I Fig. 6 showsschematically a system cderived as an extension of-the systemsof Figs.3'and'5.. 1 i f In Fig-f1. are .shox vnthe'esseiitials of a' 'fa-;

modification of thee system;

step-.by-ctep i miliar form of a push-pull.circuit,.-the fila I ment andanodecurrent supply being omitted for. the sake f simplicity. LrTw-otubes 1; 2 have :their 1 respective grids 7G1. randi anodes Pl, P2 connected in push-pull by output andiinput;transformers IT, OT eachcomprising primary and secondary"windings" ITP, OTP and ITS,;OTSrespectively". The

filaments F1, FQ'are connected to a'connnon point and a midpoint'of acondenser C1 by ers- B1, B2 arealso shown. the function of which is toneutralize the inter-electrode ca pacities of the valves inknown manner.The; input is fed through thefprimary ITP- of transformer 3 IT in theusual'manner while? the output is takenfrom the secondary-0T3; of thetransformer OT 1 r I I r If it be desired 'to-increasethe: power tob''"handled by thearrangement shownin- Fig/1i then additional. tubesmaybe-connected in- I parallel with each of the' tubes Y-IJand Qa If thearrangement'be for the purpose of amplis fyingl very high"v frequenciesit--iv-ill then be advisable to reduce C1 and C2 to very loW v values:using them only as vernier con'densers since -the"capacity. of thevalves in'parallel, will withouttheladded capacities Of C1 and C2 begreater; :than :is desired -Furthr in. order to obtain. a greater rangeofwave length} adjustment than is possible by adjustment of the smallcondensers C1 and C2 and also to overcome mechanical diflicultiesarising out of the shortness of the inductance coils on these highfrequencies, it may be advantageous to resort toseries tuning as shownin in Fi s. 1 and 2 the volta c nodes have.

been ind cated by the curve V A study will show that whereas in Fig. 1there only one voltage antinode, there are two voltage antinodes in eachof the two circuits. in Fig.

namely, across the capacities C2 and Clin l the plate circuit and acrossC1 and -C3-i1i the grid circuit. Further it will be seen on examinationof Fig. 2 that boththe input and output "circuits. become symmetricalabout lines thr h the centre points of their indnetanoe 0011s when thevalues of. C3 and C4 1 are equal respectively to the values of C1 and C2together with their respective paralleltube capacities. Thissuggests-the possibility of feeding power into the outputcirs cuitacroas(34in the samemanner as it is fed 1 in from the tubesconnected across C2and'of-r exciting the grids of thetubesby. the voltage across-C3 inthesame manner as the tubes. shown in Fig. 2 are excited by the. voltage.

across C1. Furthermore, the phase. relations are such-thatthe. tubesexcited by the voltage across C3 could feed into the outputicircuitacross C4. adding to the power delivered'by those already shown.

In accordance with the present invention therefore the condensers C3'andC4 are re-' placed by a second group of tubes in pushpull. The resultingcircuitis shown in Fig; 3 wherein voltagev nodesoccur at the pointsmidway between the inductance coils on each side ofthe tuned input andoutput circuits. Fine adjustment of tuning-is made by variation ofeitherC1 or C1 in :the grid circuit and variation of either Gator C2 in theanode circuit. It is possible by. varying the relative magnitudes of C1and C1, while fended which-are necessary to enable the load to beequally divided betwe'en the two" groups oftubes. Although the outputcircuit has been shown inductively coupled to the load it could also becoupled by capacity as shown in Figs.

lt 'will now be evident that with an arrangement such as that shown inFig. 3 the number of tubes it is possible to use. inparallel has beenquadrupled since it is now possible to use three or four in. parallel ineach corner thus making av total of twelve or sixteen. A circuit of thistype is particularly useful in the radio frequency amplification ofultra short waves namely, those having a wave length of less than 100meters.

If new the balancing condensers and filament circuit'be omitted for thesake of simplicity, it will be realized that Fig. 3 may be redrawn asshown in Fig. rion "of this circuit will show that it is possible toextend it to any number of pairs of tubes provided always that theelectrical distance between each pair is always half a wave Lleugth-or amultiple thereoi- Fig. 6 shows such a circuit extended to comprise fourpairs of tubes. The system in this case resembles two artificial lineson which standingwaves are set up; there being a group of tubes at everyvoltage loop. One of the artificial lin'es'feeds the grids and the otherreceives power from the anodes. The power capacities with the tuningcapacities in parallel form theparallel capacities of the lines and thetuningcoils form'the series inductances of the artificial. lines. Analternative ar mngement would be to insert the tuning con densers inseries with the tuning coils insteadof in parallel as shown in Fig. 6.

What is claimed is: 1 1. A-circuit for translating electrical enorgy inwhich a plurality of groups of electron tubesare provided connected inpushpull the successive groups being separated one from the other by anelectrical distance equal to one half wave length or an integralmultiplethereof.

2. A circuit for translating electrical energy comprising two artificiallines one feeding the grids of a plurality of groups of tubesinpush-pull and the other receiving power from the anodes of the saidtubes and in which the shunt impedances of the said line comprise theinterelectrode capacities of the tubes together'with associatedbalancing and tuning capacities inserted at anti-nodal voltage pointsalong the said lines.

3;; A radio frequency amplifying circuit comprising a plurality ofpush-pull ampli-' fying system's connected at successive voltageanti-nodal points in an output circuit common to all of said systems.

4. A- circuit in which an assembly of electron discharge tubes inpush-pull relation is connected in push-pull relation with anothersimilar assembly. I I

5. A circuit in which a plurality of assem- An examina- Ill blieseachcomprising a plurality of tubes-in push-pull relation are connected inpushpull relation with a plurality of similar assemblies.

Tn witness whereof. I hereunto subscribe myname this 18th day of August,1930.

CHARLES E. STRONG."

